Feat: Add configurable font setting and fix Windows font fallback

Added extension options page and configurable font settings. Fixed font fallback issue on Windows.

options.js

@@ -0,0 +1,27 @@
+// options.js
+
+// Save options to browser.storage
+const saveOptions = () => {
+  const font = document.getElementById('font-family').value;
+  
+  browser.storage.sync.set(
+    { userFont: font }
+  ).then(() => {
+    // Visual feedback
+    const status = document.getElementById('status');
+    status.style.opacity = '1';
+    setTimeout(() => {
+      status.style.opacity = '0';
+    }, 1500);
+  });
+};
+
+// Restore options from browser.storage
+const restoreOptions = () => {
+  browser.storage.sync.get('userFont').then((result) => {
+    document.getElementById('font-family').value = result.userFont || '';
+  });
+};
+
+document.addEventListener('DOMContentLoaded', restoreOptions);
+document.getElementById('save').addEventListener('click', saveOptions);